Lesser crested tern (Sterna bengalensis)
|Also known as:||crested tern, lesser crested-tern|
|Size||Length: 35 - 43 cm (2)|
Wingspan: 88 - 105 cm (2)
|Weight||185 - 242 g (2)|
The lesser crested tern is classified as Least Concern (LC) on the IUCN Red List (1).
A typical tern in appearance, the lesser crested tern (Sterna bengalensis) has uniform grey upperparts, with a black cap and crest and white underparts that are occasionally tinged with pink. The downward curving bill of this medium-sized tern is orange-yellow with a yellow tip, while the legs and feet are black with yellow webs. The iris is brown. Outside of the breeding season, the lesser crested tern has a patch of white on the forehead and crown, and the bill is yellower (2).
The lesser crested tern resembles the great crested tern (Sterna bergii), but is smaller, with a proportionately longer, slimmer and orange rather than dull yellow bill. It also differs from most other terns in having a grey rather than white tail. The juvenile lesser crested tern has heavy black spotting on the upperparts and a dusky grey band across the upper-wing coverts (2).
An elegant seabird with a fast and graceful flight, the lesser crested tern is also capable of maintaining a sustained hover. It has a slender form, the wings taper to a point and the tail is deeply forked (3).
The lesser crested tern breeds around subtropical coastlines, mainly from the Red Sea, across the Indian Ocean to the western Pacific and Australia. Another population occurs on two islands off the coast of Libya in the southern Mediterranean (4), and there are also some records of this species breeding in Spain and Italy (5).
Outside of the breeding season the lesser crested tern is also found along the Mediterranean and Atlantic coastlines of North Africa, around most of the Indian Ocean and in the western Pacific north of Australia, up to New Guinea and Vietnam (4) (6).
The lesser crested tern forages over coastal waters near sandy beaches and estuaries, and breeds on offshore islands, sandbanks and flat, sandy beaches (2) (4).
Foraging at high tide in mid-morning or late afternoon, no further than six kilometres from the coast, the lesser crested turn feeds almost exclusively on fish, supplemented by squid and crustaceans (7). It forages alone or in mixed-species flocks of up to 400 birds, catching its prey by dipping the bill into the water whilst in flight, or by plunge-diving and submerging the whole body after a short hover in the air (2).
The lesser crested tern breeds in large, dense colonies of up to 20,000 pairs, often with other tern species. The nest is no more than a shallow, unlined scrape on an exposed ridge or a bare area surrounded by vegetation (2) (4). A single egg, rarely two, is laid and incubated for 21 to 26 days. The pale, black-spotted chick is led from the nest two to four days after hatching and is fed by the adults outside of the colony. After seven days, the chicks gather in crèches that are protected by the adults. The chicks fledge at 30 to 35 days, becoming fully independent at 5 months of age and first breeding at around 2 years (2).
With a very large range and a large population that is currently thought to be stable, the lesser crested tern is not considered to be threatened with extinction (4). However, the very small European breeding population is potentially vulnerable to threats that typically affect small populations, such as disease, extreme weather events and subtle changes to habitat (5).
The lesser crested tern is listed on Appendix II of the Convention on Migratory Species (CMS) (8), and is also protected under the African-Eurasian Waterbird Agreement (AEWA), which calls upon parties to undertake conservation actions for bird species that depend on wetland habitats for at least part of their annual cycle (9).
More information on the lesser crested tern and other bird species:
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- Coverts: small feathers concealing the bases of larger flight feathers, usually on the wings or tail.
- Crustaceans: diverse group of animals with jointed limbs and a hard chitinous exoskeleton characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps and barnacles.
- Incubate: to keep eggs warm so that development is possible.
IUCN Red List (January, 2011)
- del Hoyo, J., Elliott, A. and Sargatal, J. (2001) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
- Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
BirdLife International (January, 2011)
- Burfield, I. and van Bommel, F. (2004) Birds in Europe: Population Estimates, Trends and Conservation Status. BirdLife International, Cambridge, UK.
Diomedia – Seabird Research in the Central Mediterranean (January, 2011)
Biodiversity Explorer – Lesser crested tern (January, 2011)
Convention on the Conservation of Migratory Species of Wild Animals (January, 2011)
Agreement on the Conservation of African-Eurasian Migratory Waterbirds (January, 2011)